question about judgment

My husband has a judgment against him for child support that is being garnished from his pay for the last 7 years for current and past due. I believe his ex is collecting welfare and he in return is paying back the state ( i totally agree that he should pay this) but.....i dont think it should ruin him the meantime. Is there anyway to dispute this? or could she agree to stop collecting welfare and they could settle this by themselves? I know that he would be responsible to paying off the past due still. But they're taking 600 biweekly and it's not making a dent in the past due. And my last question is how long does this judgment stay on his CR 7 years or until the past due is paid off? Please i need some advice on how to take care of this.